The interaction of age in chronic neuroleptic drugs on rat behavior and brain biochemistry is being investigated in a series of experiments. Rats of three age groups are given a one to two month period of chronic injections with fluphenazine, haloperidol and saline and studies are done at one or more time points after termination of chronic drug administration. The studies are investigating both stereotyped behavior and locomotor activity in response to dopamine agonists, and biochemical measures of receptor binding, catecholamine uptake, and HVA. Since tardive dyskinesia, a long term side-effect of chronic administration of neuroleptics in man, is more prevalent in older-age psychiatric patients, this research may provide important information about the reason for the increased prevalence of tardive dyskinesia in the older age group and the biochemical mechanisms underlying tardive dyskinesia in man.